The importance of imparting flame retardant properties to building materials, textiles, paper and other fibrous materials, and in fact any flammable object or composition in the interests of human safety, economy and energy conservation has of course long been recognized. Recently, however, the importance of such flame retardant properties has been augmented and in many instances made mandatory by legislation setting elevated standards of fire retardancy for many materials such as bedding, draperies and textiles.
It is usually not practical, and often not possible, to make flammable materials completely fire-proof. This is particularly true of textiles, paper and other materials composed of fibers which have such relatively large surface areas available for oxidation. Steel is normally considered nonflammable, but one of the most popular types of tinder used by Boy Scouts is fine steel wool, the enormous surface area of which promotes its rapid oxidation (burning). Presently available material and synthetic organic fibrous materials are of course even more flammable and will under some circumstances burn depite the use of any known expedients intended to render them non-flammable. Such expedients are thus properly referred to as directed towards reducing flammability, and terms such as flame resistant, flame retardant, and self-extinguishing are properly used rather than fireproof and nonflammable.
It will accordingly be understood that as employed herein, the term "fire retardant" or equivalent refers to a composition or property thereof which "enables a material to resist burning when exposed to a relatively low-energy ignition source, such as cigarette, match, candle, cigarette lighter, or stove burner." "Flame Retardants--government regulations and public emphasis on safety provide the importance for an expanding industry," Chemical and Engineering News, Apr. 24, 1978, pp. 22-36, 23.
May chemicals have been heretofore proposed and/or used as flame retardants. Probably one of the best known of these chemicals has been tris-(2,3-dibromopropyl)phosphate, commonly referred to as Tris. Although previously widely employed as a flame retardant for children's sleepwear, such use has been interdicted as a result of tests indicating that this compound might have carcinogenic properties.
A wide variety of other known fire retardant chemicals and combinations thereof have been and are being employed to both fill the gap left by the interdicted Tris and for all the other known uses for such chemicals but for the most part they have not been entirely satisfactory and have been subject to one or more deficiencies, for example with respect to optimal stability in storage and/or use, viscosity, water resistance and flame and/or smoke retarding properties of the flammable materials being treated, and the like. Thus, some commonly employed flame retardants such as the ammonium and alkali metal (sodium, potassium, etc.) chlorides, bromides, borates, arsenates, phosphates, polyphosphates, phosphonates, polyphosphonates and the like are more or less water soluble whereby flammable materials treated therewith or otherwise containing the same have significantly non-durable flame retardancy because of leaching under the influence of laundering, rain and other environmental conditions.
U.S. Pat. No. 3,877,974 issued Apr. 15, 1975, to V. Mischutin and assigned to the White Chemical Corporation (which markets Caliban.RTM. F/R P.RTM.-44 fire retardant) is directed to a method of rendering flammable textile materials flame retardant by treatment with an aqueous latex containing an aqueous dispersion of a fire retardant composition consisting essentially of a brominated organic aromatic or cyclic compound and a metallic oxide, such as antimony oxide, both of which are finely divided, substantially totally insoluble in water and solid at room (e.g. ambient) temperature. This method, although said to deposit on the textile an effective amount of flame retardant durable to laundering and dry cleaning, is disadvantageous in several respects. The solid particles of fire retardants in the aqueous dispersion tend to agglomerate and/or sedimentate, causing numerous problems such as instability in shipping and storage, clogging of pipes, valves, and spray nozzles, etc. The aqueous dispersion is sensitive to low temperature conditions, i.e. freezing conditions in shipping, storage and use. The aqueous dispersion is for some purposes "overformulated", e.g. antimony oxide is not needed to render polyester fibrous material flame retardant. The aqueous dispersion of flame retardant compounds cannot as such be employed for making intrinsically flame retardant materials, e.g. by inclusion in non-aqueous solid or liquid polymer compositions for coating, spinning into fibers and filaments, potting, encapsulating, molding or casting into sheets, foams, and other solid articles, etc. The low watery viscosity of the aqueous dispersion renders it unsuitable for many applications requiring relatively higher viscosities to prevent undesirable penetration as in back treatment or coating of carpets, garments, drapes and the like. Flammable materials treated with these high melting solid fire retardant chemicals do not generally have the flexibility required in many uses at ambient, and especially at relatively low, temperatures, such as wire coatings and laminations, apparel, and the like. The halogen content of this patented composition is not as high as could be desired and is further limited to bromine atoms.